Make PostRuntimeSetting pure virtual

Bug: b/177830919
Change-Id: I92e30e9b65c8f851444268f0824a676044504814
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/206640
Reviewed-by: Alessio Bazzica <alessiob@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33252}
diff --git a/modules/audio_processing/include/audio_processing.h b/modules/audio_processing/include/audio_processing.h
index 72f146f..67b9fc1 100644
--- a/modules/audio_processing/include/audio_processing.h
+++ b/modules/audio_processing/include/audio_processing.h
@@ -534,8 +534,7 @@
 
   // Enqueues a runtime setting. Returns a bool indicating whether the
   // enqueueing was successfull.
-  // TODO(b/177830919): Change this to pure virtual.
-  virtual bool PostRuntimeSetting(RuntimeSetting setting) { return false; }
+  virtual bool PostRuntimeSetting(RuntimeSetting setting) = 0;
 
   // Accepts and produces a 10 ms frame interleaved 16 bit integer audio as
   // specified in |input_config| and |output_config|. |src| and |dest| may use